Digital BW, The Print

Yes, Tony is right about Sodium sulphite (or sulfite in the US). Most of the concern of its solvent action regards the developer, where it is usually more concentrate. However, its bleaching action occurs also in the fixing step. If you use an intermediate bath between developer and fixer to minimize carry on of the former into the latter, you dont need to worry about Ph of the solution. Sodium thiosulphate is a salt, rather than an acid as the sulphite, and it will not attack unexposed silver, no matter how long you keep the film in it. 

Ciao,

   Mantinieri

www.mantinieri.com

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Tony Sleep <TonySleep@...> wrote:
>
> On 21/09/2010 Clayton Price wrote:
> > I believe you are mistaken about sodium sulfate being the ingredient
> > that removed some of the silver, since it's found in both the 
> > developers
> > and fixers
> 
> Silver sulphite (not sulphate, unused in B&W AFAICR) is a silver solvent 
> especially used in fine-grain developers to restrain grain clumping. 
> Potassium bromide is a restrainer, used to restrain fog arising through 
> dev of unexposed silver.
> 
> Used together in the correct balance they have a complementary action, 
> with bromide allowing development to proceed further (realising better 
> speed/sensitivity from the material) without undue fog, and sulphite 
> restraining graininess by dissolving some of the image silver as it is 
> formed by dev. Add local exhaustion of diluted dev in developed areas and 
> you got compensation (progessive compression of highlights, in negs) and 
> also adjacency effects that enhanced apparent sharpness.
> 
> I quite often added both to HC110 to soften its rather gritty grain.
> 
> Sulphite + KBr in print devs was a good part of the reason for the nasty 
> olive green tinge and mediocre DMax that many papers produced after 
> environmental concerns and the Bunker Hunt swindle reduced silver content.
> 
> Sulphite will attack image silver with a bleaching action, if given long 
> enough. You're correct its presence in fixer was to maintain acidity, but 
> it also meant fixing had to be as brief as was necessary to clear 
> undeveloped halide, before it started munching away at print highlights.
> 
> Now back to the dratted SATA problems I'm having, which are not so much fun...
> -- 
> Regards
> 
> Tony Sleep
> http://tonysleep.co.uk
>